Effect of Concentration and Nozzle-Collector Distance on the Morphology of Nanofibers

2020 ◽  
Vol 860 ◽  
pp. 315-319
Author(s):  
Iim Fatimah ◽  
Tri Ilma Sari ◽  
Dicky Anggoro
Keyword(s):  
Electric Field ◽  
Morphological Analysis ◽  
Electrostatic Force ◽  
Solution Concentration ◽  
Electrospinning Process ◽  
Feed Flow Rate ◽  
Dc Voltage ◽  
Solution Conductivity ◽  
Volatility Surface ◽  
Pva Solutions

Electrospinning is a method for making nanofibers by utilizing an electric field produced by high voltage. Electrospinning process is influenced by several factors including the concentration of the solution, conductivity, viscosity, volatility, surface tension, electric field strength between the needle and the collector, feed / flow rate and environmental conditions which include temperature, humidity and air composition. Electrospinning parameters are used to optimize the size of the nanofiber, concentration of the solution and the distance of the nozzle to collector. In the process of electrospinning PVA solutions that are handled by high dc voltage gets an electrostatic force and electric field. The solution will elongate to form a Taylor cone, then a jet of polymer will undergo thinning and evaporation to form fibers in the collector. The results of morphological analysis using scanning electron microscopy (SEM) showed that the smallest nanofiber was obtained at a solution concentration of 5%, dc high voltage10 kV, and the distance of the nozzle to collector was 15 cms.

Nanofibrous morphology of electrospun chitosan nanocomposites reinforced with WS2 nanotubes: A design-of-experiments study

2017 ◽  
Vol 48 (1) ◽  
pp. 119-145 ◽  
Author(s):  
Apostolos Baklavaridis ◽  
Ioannis Zuburtikudis ◽  
Costas Panayiotou
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Polymer Solution ◽  
Electric Field Strength ◽  
Response Surface ◽  
Solution Concentration ◽  
Electrospinning Process ◽  
Electron Microscopic ◽  
Inorganic Nanotubes ◽  
The Individual

Chitosan nanofibers reinforced with tungsten disulfide inorganic nanotubes (INT-WS2) were fabricated in this study. The aim was to investigate the effect of the material parameters and the electrospinning process parameters on the obtained nanofibrous morphology of the mats. The INT-WS2 content, the polymer solution concentration, the electric field strength, and the solution's flow rate were the investigated factors within the framework of response surface methodology. Scanning electron microscopic and image analysis were used for the dimensional characterization of the nanofibrous morphology and the estimation of three selected responses. Two responses were related to the quality of the nanofibrous morphology: the number surface density of the beads ( Nbead) and the average bead-to-fiber diameter ( Dbead/ Dfiber). The third response was indicative of the fiber thickness ( Dfiber). The developed models as well as the coupling and the individual effects of the four investigated factors are given. The results indicate that the electrospun nanofibrous morphology is mostly affected by the polymer solution concentration, the electric field strength and the INT-WS2 loading. Furthermore, the response-surface results reveal possible experimental pathways that may be followed in order to obtain specified nanofibrous chitosan/INT-WS2 morphologies.

Deposition Characteristics of Direct-Write Suspended Micro/Nano-Structures

2009 ◽  
Vol 60-61 ◽  
pp. 439-444 ◽  
Author(s):  
Gao Feng Zheng ◽  
Ling Yun Wang ◽  
Hong Lian Wang ◽  
Dao Heng Sun ◽  
Wen Wang Li ◽  
...  
Keyword(s):  
Electrostatic Force ◽  
Near Field ◽  
Surface Tension Force ◽  
Solution Concentration ◽  
Water Evaporation ◽  
Direct Write ◽  
Nano Structure ◽  
Electrical Field Strength ◽  
Motion Speed ◽  
Micro Pillars

Direct-Write (DW) technology based on Near-Field Electrospinning (NFES) was introduced to fabricate suspended micro/nano-structure on pattern substrate, and the deposition behaviors of DWed structure under different collector motion speed (CMS) were discussed to improve control of DW technology based on NFES. Deposit point of DWed structure on the substrate can be controlled accurately under the observation of microscope, and position error of micro/nano-structure is less than 5µm. When CMS is compatible with the electrospinning speed, straight line micro/nano-structure can be direct-written across micro-trenches with width of 5~40µm or to bridge two micro-pillars with diameter of 10µm. Due to the water evaporation and surface tension force, DWed structures suspended in the air would shrink smaller compared with that deposited on the top surface of pattern. The shrink ratio of micro-structure is higher than nano-structure and the shrink ratio decreases with the solution concentration increases. When the CMS is lower than electrospinning speed, the electrostatic force and elastic force would play a more prominent role on the deposition behavior of DWed structure. The electrical field strength on the top surface of pattern is higher than the space between two patterns, DWed thin film would deposit along the trip pattern and nanofiber would prefer to aggregate on the top surface of pattern under electrostatic force. When solution concentration is lower than 18%, nanofiber aggregate on the pattern would coagulate to form polymer bundle.

Electrostatic Forces on Particles Floating Within the Interface Between Two Immiscible Fluids

2007 ◽  
Author(s):  
Nadine Aubry ◽  
Pushpendra Singh
Keyword(s):  
Dielectric Properties ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
External Electric Field ◽  
Capillary Force ◽  
Electrostatic Force ◽  
Immiscible Fluids ◽  
Electrostatic Forces ◽  
Dipole Interactions

The objective of this paper is to study the dependence of the electrostatic force that act on a particle within the interface between two immiscible fluids on the parameters such as the dielectric properties of the fluids and particles, the particle’s position within the interface, and the electric field strength. It is shown that the component of electrostatic force normal to the interface varies as a2, where a is the particle radius, and since in equilibrium it is balanced by the vertical capillary force, the interfacial deformation caused by the particle changes when an external electric field is applied. In addition, there are lateral electrostatic forces among the particles due to the dipole-dipole interactions which, when the distance between two particles is O(a), vary as a2, and remain significant for submicron sized particles.

Joule Heating Induced Temperature Gradient Focusing for Microfluidic Concentration of Samples

2010 ◽  
Author(s):  
Zhengwei Ge ◽  
Chun Yang
Keyword(s):  
Temperature Gradient ◽  
Electric Field ◽  
Joule Heating ◽  
Field Experiments ◽  
Dc Voltage ◽  
Sample Concentration ◽  
Great Achievement ◽  
Temperature Gradient Focusing ◽  
Concentration Enhancement ◽  
High Frequency Ac

Microfluidic concentration of sample species is achieved using the temperature gradient focusing (TGF) in a microchannel with a step change in the cross-section under a pure direct current (DC) field or a combined alternating current (AC) and DC electric field. Experiments were carried out to study the effects of applied voltage, buffer concentration and channel size on sample concentration in the TGF processes. These effects were analyzed and summarized using a dimensionless Joule number that is introduced in this study. In addition, Joule number effect in the Poly-dimethylsiloxane (PDMS)/PDMS microdevice was compared with the PDMS/Glass microdevice. A more than 450-fold concentration enhancement was obtained within 75 seconds in the PDMS/PDMS microdevice. Results also showed that the high frequency AC electric field which contributes to produce the temperature gradient and reduces the required DC voltage for the sample concentration. The lower DC voltage has generated slower electroosmotic flow (EOF), which reduces the backpressure effect associated with the finite reservoir size. Finally, a more than 2500-fold concentration enhancement was obtained within 14 minutes in the PDMS/PDMS microdevice, which was a great achievement in this TGF technique using inherent Joule heating effects.

A New Design of Large Stroke Micro-Deformable Mirror Actuated by Electrostatic Repulsive Force

2008 ◽  
Author(s):  
Fangrong Hu ◽  
Jun Yao ◽  
Chuankai Qiu ◽  
Dajia Wang
Keyword(s):  
Electric Field ◽  
Resonant Frequency ◽  
Adaptive Optics ◽  
Bottom Electrode ◽  
Sacrificial Layer ◽  
Electrostatic Force ◽  
Repulsive Force ◽  
Deformable Mirror ◽  
Optical Aberrations ◽  
Out Of Plane

In this paper, a MEMS mirror actuated by an electrostatic repulsive force has been proposed and analyzed. The mirror consists of four U-shape springs, a fixed bottom electrode and a movable top electrode, there are many comb fingers on the edges of both electrodes. When the voltage is applied to the top and bottom electrodes, an asymmetric electric field is generated to the top movable fingers and springs, thus a net electrostatic force is produced to move the top plate out of plane. This designed micro-mirror is different from conventional MDM based on electrostatic-attractive-force, which is restricted by one-third thickness of the sacrificial layer for the pull-in phenomenon. The characteristic of this MDM has been analyzed, the result shows that the resonant frequency of the first mode is 8 kHz, and the stroke reaches 10μm at 200V, a MDM with large strokes can be realized for the application of adaptive optics in optical aberrations correction.

scholarly journals A Novel Capacitive Sensing Principle for Microdevices

2015 ◽  
Author(s):  
Jian Zhou ◽  
Ronald N. Miles ◽  
Shahrzad Towfighian
Keyword(s):  
Electric Field ◽  
Driving Force ◽  
Design Principle ◽  
Electrostatic Force ◽  
Low Cost ◽  
Repulsive Force ◽  
Attractive Force ◽  
Sensor Design ◽  
Capacitive Sensing

Conventional capacitive sensing places significant limitations on the sensor design due to the pull-in instability caused by the electrostatic force. The main purpose of this study is to examine a low-cost novel capacitive sensing principle based on electrostatic balance which promises to avoid these design limitations. The approach uses an asymmetric electric field on a structure with fingers that can generate a repulsive force while the gap is low and create an attractive force while the gap is large. The size and thickness of the fingers are also responsible for creating repulsive or attractive forces on the structure. This approach has recently been applied successfully in the design of capacitive actuators to provide a repulsive driving force. A new design principle for capacitive sensing is described that avoids pull-in instability by designing the fingers such that the structure is at the equilibrium.

Numerical Simulation of Viscous Jet for Near-Field Electrospinning

2009 ◽  
Vol 60-61 ◽  
pp. 465-469 ◽  
Author(s):  
Yuan Yuan Zhong ◽  
Gao Feng Zheng ◽  
Dao Heng Sun
Keyword(s):  
Numerical Simulation ◽  
Field Strength ◽  
Process Parameters ◽  
Near Field ◽  
Solution Concentration ◽  
Electrospinning Process ◽  
Substrate Distance ◽  
Viscous Jet ◽  
Set Up ◽  
The Impact

Near-Field Electrospinning (NFES) is a newly developed method to fabricate continuous and ordered solid nanofibers, with smaller spinneret-to-collector-distance the behavior of viscous jet would play a more prominent effect on the deposition and morphology of nanofiber. In this paper, a 2-dimentional physical model based on electrohydrodynamics and rheology was set up to discuss the morphology of viscous jet for NFES. The profile of the jet along z direction can be predicted by this model, and the impact of process parameters on the jet radius is analyzed. Radius of jet decreases with spinneret-to-substrate-distance decreasing; jet radius decreases with applied voltage and electric field strength increasing; jet electrospun from PEO solution is thinner than that from PVA solution with the same solution concentration; solution concentration has insignificant influence on the radius of jet from solution of the same polymer (PVA or PEO). This numerical simulation would improve the control of electrospinning process in NFES.

Direct Simulation of Electrorheological Suspensions

2001 ◽  
Author(s):  
Aijun Wang ◽  
Pushpendra Singh ◽  
Nadine Aubry
Keyword(s):  
Electric Field ◽  
Stokes Equations ◽  
Hydrodynamic Force ◽  
Particle System ◽  
Electrostatic Force ◽  
Body Motion ◽  
Three Dimensions ◽  
Spherical Particles ◽  
Point Dipole ◽  
Direct Simulation

Abstract A new distributed multiplier/fictitious (DLM) domain method is developed for direct simulation of electrorheological (ER) suspensions subjected to spatially uniform electrical fields. The method is implemented both in two and three dimensions. The fluid-particle system is treated implicitly using the combined weak formulation described in [1,2]. The governing Navier-Stokes equations for the fluid are solved everywhere, including the interior of the particles. The flow inside the particles is forced to be a rigid body motion by a distribution of Lagrange multipliers. The electrostatic force acting on the polarized spherical particles is modeled based on the point-dipole approximation. Using our code we have studied the time evolution of particle-scale structures of ER suspensions in channels subjected to the pressure driven flow. In our study, the flow direction is perpendicular to that of the electric field. Simulations show that when the hydrodynamic force is zero, or very small compared to the electrostatic force, the particles form chains that are aligned approximately parallel to the direction of electric field. But, when the magnitude of hydrodynamic force is comparable to that of the electrostatic force the particle chains orient at an angle with the direction of the electric field. The angle between the particle chain and the direction of the electric field depends on the relative strengths of the hydrodynamic and electrostatic forces.

Discharge and Flashover Behavior in Oil-Paper

2020 ◽  
pp. 105-128
Keyword(s):  
Electric Field ◽  
Operating Conditions ◽  
Surface Discharge ◽  
Discharge Characteristics ◽  
Dc Voltage ◽  
Composite Field ◽  
Field Distortion ◽  
Lightning Impulse ◽  
Creeping Discharge ◽  
Paper Insulation

Due to special operating conditions, the valve side bushing of the converter transformer connected to the converter valve is subject to complex voltage excitation, including DC voltage, AC/DC composite voltage, lightning impulse overvoltage, or composite voltage of operating overvoltage and DC. Under the action of this complicated electric field, the oil-paper insulation of the valve-side bushing of the converter transformer is prone to electric field distortion due to charge accumulation, which causes a surface discharge, which will seriously cause the edge breakdown. At the same time, since the temperature in the converter transformer rises due to a large amount of loss during the operation of the transformer, creeping discharge is more likely to occur under the electrothermal composite field. Hence, it is significant to carry out research on the surface discharge characteristics of the oil-paper insulation on the valve side of the converter transformer under the electrothermal composite field.

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